Rotary blood pump

Abstract

The present invention provides a rotary blood pump with both an attractive magnetic axial bearing and a hydrodynamic bearing. In one embodiment according to the present invention, a rotary pump includes an impeller assembly supported within a pump housing assembly by a magnetic axial bearing and a hydrodynamic bearing. The magnetic axial bearing includes at least two magnets oriented to attract each other. One magnet is positioned in the spindle of the pump housing while the other is disposed within the rotor assembly, proximate to the spindle. In this respect, the two magnets create an attractive axial force that at least partially maintains the relative axial position of the rotor assembly. The hydrodynamic bearing is formed between sloping surfaces that form tight clearances below the rotor assembly.

What is claimed is: 
     
       1. A method of pumping blood comprising:
 providing a pump housing defining a pump chamber having an inlet and an outlet and a rotor rotatably disposed in said pump chamber; 
 spinning said rotor 
 generating a hydrodynamic bearing between said pump housing and said rotor using a plurality of a plurality of lifts positioned between said pump housing and said rotor; each of said plurality of lifts being elongated and sloped at an angle relative to a pump chamber surface such that each of said plurality of lifts includes a first planar surface extending at an angle relative to a pump chamber surface and a second planar surface, connected to said first surface, extending substantially parallel to said pump chamber surface; and, 
 supporting said rotor with a passive axial magnetic bearing comprised of a pump housing magnet and a corresponding rotor magnet wherein magnetic fields of said pump housing magnet and said corresponding rotor magnet are oppositely aligned in the axial direction; 
 said hydrodynamic bearing and said passive axial magnetic bearing cooperating with each other so as to enhance axial stability to said rotor during rotation of said rotor. 
 
     
     
       2. The method of pumping blood according to  claim 1 , wherein, said first surface is angled from said pump chamber surface between about 0.5 degrees and about 3 degrees. 
     
     
       3. The method of pumping blood according  claim 1 , wherein said each of said plurality of lifts is disposed on said rotor. 
     
     
       4. The method of pumping blood according to  claim 1 , wherein each of said plurality of lifts is disposed on said pump chamber surface. 
     
     
       5. The method of pumping blood according to  claim 4 , wherein each of said plurality of lifts is formed integrally on said pump chamber surface. 
     
     
       6. The method of pumping blood according to  claim 1 , wherein said plurality of lifts is comprised of at least three lifts. 
     
     
       7. The method of pumping blood according to  claim 1 , wherein said plurality of lifts constitutes a cumulative total area within a range of about 40% to 90% of said pump chamber surface area. 
     
     
       8. The method of pumping blood according to  claim 1 , wherein the plurality of lifts are sized to produce an amount of force adequate to compensate for the sum of the net hydrodynamic/hydrostatic forces of said pump plus an attractive force between a motor magnet and back iron of said pump. 
     
     
       9. The method of pumping blood according to  claim 1 , wherein said plurality of lifts are sized and shaped to produce a hydrodynamic bearing when a clearance between said pump housing and said rotor is within a range of about 0.0002 inches to 0.001 inches. 
     
     
       10. The method of pumping blood according to  claim 8 , wherein said compensatory force produced by said plurality of lifts equals at least around 1.302 pounds. 
     
     
       11. A method of pumping blood comprising:
 providing a housing assembly defining an interior pump surface and a rotor rotatably disposed in said housing assembly; 
 spinning said rotor; 
 forming a hydrodynamic bearing using a plurality of lifts positioned between said housing assembly and said rotor; each of said plurality of lifts comprised of an elongated sloping surface such that each of said plurality of lifts includes a first planar surface extending at an angle relative to a pump chamber surface and a second planar surface, connected to said first surface, extending substantially parallel to said pump chamber surface, and 
 passively supporting said rotor using a passive axial magnetic bearing comprised of a housing magnet and a corresponding rotor magnet wherein magnetic fields of said housing magnet and said corresponding rotor magnet are oppositely aligned in the axial direction 
 said hydrodynamic bearing and said passive axial magnetic bearing cooperating with each other so as to enhance axial stability of said rotor during said spinning of said rotor. 
 
     
     
       12. The method of pumping blood according to  claim 11 , wherein, said first surface is angled from said interior pump surface between about 0.5 degrees and about 3 degrees. 
     
     
       13. The method of pumping blood according to  claim 11 , wherein said each of said plurality of lifts is disposed on said rotor. 
     
     
       14. The method of pumping blood according to  claim 11 , wherein each of said plurality of lifts is disposed on said interior pump surface. 
     
     
       15. The method of pumping blood according to  claim 14 , wherein each of said plurality of lifts is formed integrally on said interior pump surface. 
     
     
       16. The method of pumping blood according to  claim 11 , wherein said plurality of lifts is comprised of at least three lifts. 
     
     
       17. The method of pumping blood according to  claim 11 , wherein said plurality of lifts constitutes a cumulative total area within a range of about 40% to 90% of said interior pump surface area. 
     
     
       18. The method of pumping blood according to  claim 11 , wherein the plurality of lifts are sized to produce an amount of force adequate to compensate for the sum of the net hydrodynamic/hydrostatic forces of said pump plus an attractive force between a motor magnet and back iron of said pump. 
     
     
       19. The method of pumping blood according to  claim 11 , wherein said plurality of lifts are sized and shaped to produce a hydrodynamic bearing when a clearance between said internal pump surface and said rotor is within a range of about 0.0002 inches to 0.001 inches. 
     
     
       20. The method of pumping blood according to  claim 18 , wherein said compensatory force produced by said plurality of lifts equals at least around 1.302 pounds. 
     
     
       21. The method of pumping blood according to  claim 1 , further comprising positioning said pump housing magnet and said rotor magnet to be offset from each other in an axial direction. 
     
     
       22. The method of pumping blood according to  claim 11 , further comprising positioning said housing magnet and said rotor magnet to be offset from each other in an axial direction.